Making a Jacob's Ladder

tazzle

tazzle

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Making a Jacob\'s Ladder

Coming back from France yesterday (on the ferry) I had a close look at the escape ladders; a MOB / boarding ladder is something I need for Radweld but can't fit a fixed one, and the pull-down Plastimo ones look toy-ish and even the Jimmy Green rope ladders are just thin round timber with single ropes. In fact I've been unable to find a good, heavy, solid rope ladder that won't easily twist.

So this is my project for weekday evenings over the next couple of weeks. Ferry ropes are doubled and look like Sisal - for stiffness, I think - and are just heavily whipped with ~3mm Marline(?) above and below each step, steps spaced at about 300mm. Guide blocks glued and screwed.

My local timber merchant does 100 x 38 Iroko for about £8/m - planed size will be a tad smaller so dims on drawing are nominal. Tradline does 20mm Sisal for £1.95/m. Classic marine does heavy duty Marline whipping. So materials cost estimate for a 6-step ladder is about £45.

Any obvious probs before I start?

jacobspw2.jpg
 
Re: Making a Jacob\'s Ladder

No, dont see any obvious problems there, we have tapered blocks top and bottom on our ladders here on the rig, to allow the whipping to pull the rope together under and above the steps, they are inline with the holes as opposed to across them as in your drawing, but I guess yours would work as well, top and bottom of course. I would also space the holes out closer to the edges of the steps, to assist anti twist, they seem to be only 25mm apart, better to be 50mm apart? I would also use smaller rope, 16mm would be ample, will stiffen with age, but the ropes dont need to be stiff. Go for it!
 
Re: Making a Jacob\'s Ladder

We used to make these onboard with manila rope. Ladders up to 10m long.

If using one of the natural ropes such as manila or sisel then I would recommend stretching the rope before making the ladder to take the natural twist out.

We would then feed the rungs on and stretch the ropes between 2 strong points using a chain block or rope tackle, then seize the steps in position with the rope under load.

As already mentioned, you could purchase all the bits from a marine supplier such as Cosalt

Hope this helps
 
Re: Making a Jacob\'s Ladder

I recess the long edges of each step around maybe 5-10 mm or so (whatever looks right) apart from 60 to 70mm or so at each end so's when it lies against the side of the hull the middle part of the step edge does not roll on the longitudinal curvature in the hull should there be any ( a problem ships don't have).

Round off all the corners and edges.

Personal only, but the steps of ours are wider so's feet better fit on them.

Unless you want to be "traditional" laid polyester makes a better line and needs only be around 10 mm dia (that dia for looks rather than strength). And, as CCScott says, be spaced further apart, in which case if you get them well apart (maybe need wider steps though) you don't need the guide blocks underneath (which add to the weight - see below).

Another way of spacing the steps is with lengths of PVC tube over the rope between each pair of steps but does not stow so conveniently and no where like traditional though - made my own that way and to stow you sort of zig zag the steps backwards and forwards so they lie on top of each other (very illustrative I know).

They are heavy and will be especially so if goin' to be 38mm thick - 20mm is more than ample and 15mm lighter still and ok. I suggest you calculate the weight beforehand to see if suits you.

Couldn't comment on Iroko but we don't find teak needs to be grooved for foot grip (but may look better if grooved).

We have a punched toerail and use snap hooks to clip our own to that.

If you have computer produced vinyl or other coating softer than gel coat or polyurethane graphics, shadow stripe, name, topsides paint, whatever on the side of the boat the wooden steps mark them/it and is visible if dark colours.

In the end one does it as one thinks it will look best for the boat.

John
 
Re: Making a Jacob\'s Ladder

Very helpful advice from all - and I'll be making a number of mods as suggested. I hadn't even thought of slightly dishing the inner edges - good thinking.

Still fancy giving the router an outing though rather than buying the steps. It hasn't had much work to do over the past few months and is feeling a bit neglected /forums/images/graemlins/grin.gif
 
Re: Making a Jacob\'s Ladder

You describe your ladder as a boarding/MOB ladder. If you're sailing in the coolish water around the UK, a ladder may not be too good for a MOB. Cold Water Shock plus physical exersion is bad, plus grip may be impaired.
 
Re: Making a Jacob\'s Ladder

JUst as another aside, our ones on the rig, are two steps wide (one pice of wood) , with three ropes, even better.
 
Re: Making a Jacob\'s Ladder

Jacobs ladders are the "monkey-ladders" that you first described. using round wood bar and inserted into lay of single rope.
Generally provided for quick use in reading ships drafts etc. - Surveyors and others are strongly advised to not use them - as they get usede on painting and other jobs.

The ladder you describe of steps set between two sisal or manila ropes are Boarding Ladders - of traditional and statutory design. I'm not sure about now - but until I left sea - all lifeboat ropes had to be natural fibre of fixed size ... based on resistance to weather and UV etc.
The best and most strictly design controlled rope-constructed ladder on a ship is the Pilot Ladder ...... anjd for those interested about them : http://www.opsi.gov.uk/si/si1987/Uksi_19871961_en_1.htm

Go for it ......
 
Re: Making a Jacob\'s Ladder

I used 25 mm wide webbing and cut 4 slots in the end of each step. I positioned the webbing in the slots and fixed it in with a screw through the step, through the webbing and into the center of the step

I them fixed some short lenghts of plastic hose to the inside edge of esch step to protect the side of the hull.
 
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